Presser foot drive for sewing machines



Jan. 25, 1966 BECKER ETAL 3,230,915

PRESSER FOOT DRIVE FOR SEWING MACHINES Filed Oct. 25, 1962 3 Sheets-Sheet 1 Fllg. I

Fig.2 5 I ERNST BECKER RUDOLF KLlNG ATTORNEY.

Jnven/ors:

Jan. 25, 1966 E. BECKER ETAL 3,230,915

PRESSER FOOT DRIVE FOR SEWING MACHINES Filed Oct. 25, 1962 3 Sheets-Sheet 2 Fig.

Jn venfors:

ERNST BECKER RUDOLF KLING ATTORNEY.

Jan. 25, 1966 E. BECKER ETAL 3,230,915

PRESSER FOOT DRIVE FOR SEWING MACHINES 3 Sheets-Sheet 5 Filed Oct. 23, 1962 Fig. 6

ATTORNEY.

United States Patent 3 230 915 PRESSER FOOT muvls rim SEWING MACHINES Ernst Becker and Rudolf Kling, Darmstadt, Germany, assignors to Quick-Rotan Becker 8: Co., Darmstadt,

Germany Filed Oct. 23, 1962, Ser. No. 232,361

16 Claims. (Cl. 112-439 Attempts have already been made to provide means for raising and lowering a sewing machine presser foot, employing an electromagnet. A lifting magnet usable for this purpose must be so designed that the armature can lift the presser foot against the force of the presser spring. This force may be as much as twenty kilograms. For this reason, and because the armature adjustment distances are very considerable, an electromagnet of this kind has to be made relatively large. The current consumption is also significant, because the magnet has to be permanently switched on during intervals between sewing. The time required to move the presser foot is considerable due firstly to the considerable mass of the magnet and secondly to the large movements required of the presser foot.

In the drive according to the invention for raising and lowering the presser foot of a sewing machine, the presser foot is displaced by means of an electric motor, preferably through a reduction gear. In the simplest case, the arrangement is such that the displacing motor is switched on whenever the sewing machine is switched on and is switched off by way of alimit switch when the presser foot is in its position of contact (i.e. its operative position), and the displacing motor is set into reverse rotation when the sewing machine is switched off, and is switched oil by way of a second limit switch when the presser foot reaches its lifted end position (i.e. its inoperative position). A drive of this kind has the advantage that there is no current consumption during intervals between sewing. In addition, the movement times can be kept shorter and particularly if microswitches are used the overall dimensions can be kept small. The displacing motor is preferably switched on and ofi by the same ele ment used to switch the sewing machine on and ofr. The arrangement can then be such as to ensure that the presser foot .is moved into its end position of contact before the sewing operation begins and into the end position corresponding to the lifted position after the completion of the sewing operation. A straight or arcuate push crank acting on the presser foot is advantageously provided at the reduction gear. 1

Although the displacing motor gives considerable advantages if it is switched on and off as required, it is nevertheless advantageous to reduce the movement times further by allowing the displacing motor to rotate continuously and to provide a clutch by means of which the reduction gear can be connected to or separated from the displacing motor, the closure of the presser foot preferably being effected in manner known per se by spring force, and the crank drive lifting the presser foot by way of a belt or chain. The clutch used is advantageously a clutch the adjustment element of which can be operated electromagnetically. In that case, an electrical series contact may be provided on the operating element for switching the sewing machine on and off, so that the magnetic clutch circuit is closed before the sewing machine is started and is opened after the same has stopped.

To break the magnetic clutch circuit in a simple manner as soon as the presser foot reaches one or other end position, it is advisable to provide the magnetic clutch circuit with two limit position switches so disposed that one is opened whenever the presser foot reaches one or other end position.

If a continuously rotating displacing motor is used in conjunction with a clutch, the displacing motor will admitte/dly use current during intervals between sewing but this consumption is so low as to be practically negligible, since when the presser foot is lifted the displacing motor need not perform any work and accordingly consumes only the no-load current. If this insignificant current consumption is accepted, the particular advantage obtained is that the presser foot drive is always ready for operation. Another favourable efiect is that the displacing motor always rotates in the same direction of rotation.

To enable the limit position switch to be switched off in simple manner it is advantageous to allow the reduction gear to drive not only the crank drive for operation of the presser foot but also a switch cam for opening the limit position switches, the latter being so disposed at an angle in relation to the switch cam that they open when the presser foot reaches one or other end position.

It the presser foot is to be stopped in a position between its end positions, this is possible immediately by using an additional switch operable by the switch cam. In this case, there is advantageously provided a manually opera ated electric switch which normally bridges the additional switch but which allows the additional switch to become operative when actuated.

To ensure that the reduction gear is instantaneously stopped when the clutch circuit is broken, it is advanta geous to provide a brake which is applied automatically when the clutch has been released from the displacing motor and is automatically released when the clutch is connected to the motor. The brake may be spring-loaded and respond electrically. This is extremely simple if the brake circuit is opened and closed by the switch cam. To this end the arrangement may be such that the bridge for the limit position switches and for the additional switchare moved into a position to close the brake circuit when the clutch circuit is opened.

simplified if, according to a further feature of the invention, the sewing machine driving motor additionally performs the function of the displacing motor, use preferably being made of a driving motor which enables the sewing machine to stop when the sewing needle is in the raised and lowered positions. Since the sewing machine driving motor will already comprise a rectifier, the latter can at the same time be used for the circuit, because the Working rhythms of the displacing motor and the driving motor do not coincide but are successive to one another.

If the sewing machine is adapted to be switched on by way of a pedal, it is advisable to allow the pedal to act through a tension element on an electrical switch which, when the pedal is released, closes the brake circuit and opens the sewing machine circuit but which, when the pedal is partially adjusted or depressed, opens the brake circuit and closes the magnetic clutch circuitand when the pedal is fully adjusted or depressed, additionally closes the sewing machine circuit. In these conditions it is advantageous for the switch operated by the tension ele ment to comprise two switch bridges, one of which is used to close and open the brake circuit and to open and close the clutch circuit, While the other bridge opens and close the sewing machine circuit.

In order to prevent the sewing machine from being switched on before the presser foot has been lowered if the pedal is moved rapidly, it is advisable to provide the sewing machine circuit with a safety switch which, on the opening of the limit position switch determining the lowered presser foot position, is switched on by the operating element of said limit position switch.

The reduction gear is advantageously constructed as a separate component which is preferablyfittedto the bott'oi'n'of the 'sewing tableandwhich accommodates, in a gearbox cover on one end, the limit position switches and the .switch cam, While a case cover at the other endaccornmodatesthe crank drive.

The space required for .the drive can be further reduce d if the magnetic clutch and reduction gear are combined to form one unit. I

The invention wil bedescribed further, by way of example, with reference to the accompanying drawings which illustrate a number of practical embodiments of 'the invention and wherein: I I

FIG. 1 is .a .front view of a first embodiment of the dfivle;

FIG. 2 'is a longitudinal section through the reduction gear used in the drive of FIG. 1; II

FIG. 3 is a rear view of the drive of FIG. 1;

FIG. 4 is a front view of a modified embodiment of the drive; I I I FIG. 5 is a lingitudinal section through the reduction gear of the embodiment of FIG. 4; and I FIG. 6 is an electrical circuit diagram of an embodiment wherein the sewing machine motor provides also the driving source for the presser foot displacing arrangement.

In the construction shown in FIGS. 1 to 3, the drive is taken from a displacing motor 1 through a pulley 2 to a clutch 3, from which, depending upon the state of engagement or disengagement of the clutch 3, it is transmitted to a reduction gear 4 and then to an arm ,5 of a foot, being converted into a longitudinal force. During operation, the motor 1 is switched on continuously and rotates constantly only in one direction. One element (not shown) of the clutch 3 driven by the motor -1 ac cordingly also rotates continuously. A second element, which is adapted to be coupled to or separated from the continuously rotating first-mentioned .clutch element, is arranged to be shifted electromagnetically, e.g. by closing and opening of a switch respectively at the commencement and end of a sewing operation, for instance by a switch operated simultaneously with a switch controlling the machine. Drive is transmitted from the said second element of the clutch 1 to a worm 6 of the reduction gear 4. The worm 6 meshes with a worm wheel 7 providedon a shaft 8 which, at one end of gearbox 9, carries a disc 10 provided with an eccentric crank pin 11, and at the other end carries a disc 12 with a switch cam 13. The crank pin 11 engages a connecting rod 14 so that on one full revolution of the disc 10 the rod 14 performs a reciprocating movement firstly in the direction t and then in the opposite direction to the arrow A of FIG. 2. The reduction gear 4 is screwed to the bottom of a sewing table 16 of a sewing machine by way of a flange 15, and the rod 14 is coupled with the presser foot arm by way of. a chain link 17. The presser toot arm 5 is urged to} wards its position of contact (i.e. its operative position) by a spring: (not shown). The arrangement is such that the presser foot is lifted as soon as the arm is moved in the directionof the arrow'A.

The reduction gear co-operates by way of the disc 12 with the. switch arm 13 with limit position switches 18 and 19 disposed in the circuit of the clutch 3. The switches 18' and 19 are so operated that the clutch circuit is broken as. soon: as the switch cam 13 presses in either of. the switch: operating elements 20 and 21. When" this isthe case, the clutch 3 is disengaged so that the drive from the motor 1 is no longer transmitted to the reduction gear 4. The gear thus stops when the limit position switches'18, 1'9are'opened. I I

In theexemplified embodiment illustrated, the" gear 4 is stopped whenever the crankpinll assumes its'bottom' or"top-dead centre*position. If it is in its bottonr dead-- centre'position in which the rod'14 has been moved in the direction of the ar'row A, thepresser foot is in its lited (oi' inoperative)position: If=thecrankpin11 is'in ,its top dead-centre position, then the spring (not shown) The crank-may be constructed as 'a straight-or arcuate .push crank.

To provide a simple constructipn for the reduction gear 4, the crank'drive 'is accommodated frontcover 22 of the gearbox 9 andthe'lirnitposition switches 18, 19 together with the disc 12 Zandthe switch cam 13 are disposed similarly in area cover 23 of the gearbox. These covers 22, 23 can "be closed by respective end plates, as shown in FIG. 2. I V

The drive -shown in FIGS. 4 and 5 is very similar to that shown in FIGS. 1 to 3 but'in this case the shaft 8 drives a double lever 25 whichis mounted at 26 'on a modified front cover-22' and which acts onthe presser foot by way of a chain 28 and a longitudinally adjustable pull rod 27 by way er an eccentric 24.

The embodiments showh iniFIGS. P1 to 3 on the one hand and FIGS. "4 and 5 on "the otherhand can easily be converted "to one another. To this end it is only'neces- 'sary to change the "from covers with their associated internal fittings. I

The adjusting motor '1 may be dispensed with if the sewing machine driving motor is adapted to perform the function thereof. FIG. '6 shows such construction diagrammatically. In this embodiment, anfe lectrically erati've brake-2 9 is provided for instantaneou s stopping of the reduction gear after the disengagement of the clutch 3,. and the brake circuit is shown in broken lines to indicate that it may be dispensed with. The supply to the brake 25 and to winding seer the magnetic clutch 3 is DL'C. furnished by rectifiers' 31 of the sewing machine driving motor. I I I I ,I I I In the condition illustrated, the brake 29 is energised. Current flows through lead 32, the brake29, switch bridge 33, switch bridge 3'4, lead 3i5, element 56 of a manually operable switch 37 and lead 38 back to the currentsource. If-pedal 39 is swung in the direction of the arrow C, then the operating element 41 of the switch 423s moved, by way of the. chain 40, in the direction of the arrow D so that the switch bridge 34 is lifted from contacts 43 and 44 so that the cii 'cuit of the brake 29 is broken. The brake is accordingly released by spring fo'rce when the dish 12 with its switch can 13 rotates again, As soonas the switch bridge 'M connects contacts 45, 46 the coil of the magnetic clutch 3 receives current so that the reduction gear rotates, moving the disc 12 for example in the direction of a'r'rowB. The switch cam 13 som quently moves away from the switch operatingelernent 20. The contacts 47 andAS are therefore connected by the'switch bridge 33 On further swingingpf the pedal 39 in the direction of the arrow C 'contacts 49am :50 are connected by switch bridge 51 on the operating element 41; whilst the connection between the whims 45 and 46 is maintained. I y I As soon: as the switch cani '13'..re'aches' the. operating element 21 the latter is move inv the direction of the arrow E so that the switch bridge, 52 breaks the supply of cuire'nt to the coil 30 of, the maghetid clutch 3 and makes cennecno'n beitwe contacts 53 and 54; The brake 29 is therebyen'er sd that the, reduction gear is instantaneously stopped after disengagement of the duress. ,I II I I e. o movement ofthe' adjusting element 21 in the direction' of'the arrows a' safety switch 55' is closed so that a magnet 56, which becomes connected to the DC. source by terminals 57, 58, is energised and serves to operate a sewing clutch (not shown) which thus couples the sewing machine to the sewing machine motor. I v I II If the switch 37, which can .be, arr nged'sd that the sewing machine" oper'itor' can actuate it by meansof her knee, is so adjusted that its switch element 36 assumes the position shown in broken lines, then as the disc 12 rotates switch bridge 59 is displaced in the direction of the arrow F so that first of all the supply of current to the coil of the magneticclutch 3 is broken and then the supply of current to the brake 29 is established.

The switch bridge 59 together with its associated contacts and its operating element constitutes an additional switch which determines an intermediate stop position of the presser foot. The manually operable switch 37, in the normal position shown in solid lines in FIG. 6, bridges the additional switch of which the switch bridge 59 forms part.

It the pedal 39 is released when the switch 37 is in the normal position shown in solid lines in FIG. 6, so that such pedal 39 is swung in the direction opposite to the arrow C under the action of a spring and hence the operating element 41 is slid in the direction opposite to the arrow D, the switch bridge 51 is first lifted from the contacts 49 and 50 so that the magnet 56 is de-energised with resultant stoppage of the sewing machine. On further displacement of the operating element 41 in the direction opposite to the arrow D, the switch bridge 34 is lifted from the contacts and 46 with resultant interruption of the supply of current to the brake 29. On yet further displacement of the operating element 41 in the opposite direction to the arrow D, the bridge 34 finally provides a connection between the contacts 43 and 44 so that the coil 30 of the clutch 3 is switched on. The switch cam 13 is therefore turned from the bottom dead-centre position into the top dead-centre position in which it moves the operating element 20 into the position shown in FIG. 6. In these conditions the current supply to the coil 30 is broken while the supply of current to the brake 29 is established.

The switch bridge 34 is an electrical series contact which on depression of the pedal 39 closes the circuit to the coil 30 before the switch bridge 51 connects the contacts 49 and and hence before the magnet 56 is energised. The sewing machine cannot, therefore, be started until the presser foot has been lowered. Premature starting of the sewing machine even in the event of rapid depression of the pedal 39 is avoided by the safety switch since the latter is not closed until the operating element 21 has been displaced by the switch cam 13 in the direction of the arrow E. Since such displacement is possible only when the crank pin 11 reaches its bottom dead-centre position and the pressure foot has been moved into its position of contact (i.e. its operative position), the sewing machine cannot be started until the presser foot has been lowered even if the contacts 49 and 50 are prematurely bridged.

The sewing machine circuit contains a closed-circuit relay including a contact in lead 61, which contact 60 is always closed when the sewing machine circuit is open. This prevents any flow of current between the contact 44 and the lead 61 if the magnet 56 is energised and reliably prevents the presser foot from being lifted before the sewing machine has been switched off by the magnet 56.

The reduction gear 4 may form a separate component or can be combined with the magnetic clutch 3 to form a structural unit.

The operation of the device may be described as follows:

In the switching state, as shown in FIG. 6, the presser foot is raised. The brake coil 29 receives current. If the pedal 39 is depressed,

(a) the brake coil 29 is de-energised because the switch 34 interrupts;

(b) the clutch magnet 30 is energised because the switch 34 closes the contacts 45, 46;

(c) the disc 12 is driven in the direction of the arrow B;

((1) connection is established between the contacts 47, 48

because the cam 13 moves away from the switch operating element 20;

(e) the contacts 49, 50 are short-circuited by the switch element 51;

(f) the magnetic clutch is de-energised because the cam 13 moves to the switch operating element 21 and interrupts, so that the brake 29 is energised because the contacts 53, 54 are short-circuited by the switch bridge 52, the disc 12 is stopped and the presser foot is lowered;

(g) the switch element 55 is closed, and the magnet 56 is excited so that the sewing machine is set going.

If the pedal 39 is released,

(a) the switch 51 is opened, the magnet 56 de-energised,

and the sewing machine stops;

(b) connection between contacts 45 and 46 is interrupted so that the brake 29 is de-energised;

(c) the contacts 43 and 44 short-circuited by switch bridge 34 so that magnet 30 is energised;

(d) the disc 12 rotates so that the cam 13 moves from its lowest position to its highest position as shown in FIG. 6, the switch 33 connects the brake 29 to the current source, and the presser foot is raised.

In the position shown, the toggle switch 36, 37 shortcircuits the switch 59. When the switch 37 is moved to the broken line position, the switch 59 becomes effective. When the cam 13 actuates the latter the clutch 30 is deenergised and the brake magnet 29 energised so that the disc 12 stops and the presser foot stays in an intermediate raised position.

We claim:

1. In a sewing machine, an automatic presser foot shifting mechanism rendered operative as the sewing machine is switched into operating condition and inoperative as the sewing machine is switched into non-operating position and adapted for actuation by a motor rendered operative by a pedal-actuated electromagnetic clutch, the combination therewith of, a series-connected reduction gear unitary with the electromagnetic clutch, an output shaft driven by and extending from said reduction gear, a presser foot actuating member, and a straight crank drive intermediate and interconnecting said output shaft and presser foot actuating member.

2. In a sewing machine, an automatic presser foot shifting mechanism rendered operative as the sewing machine is switched into operating condition and inoperative as the sewing machine is switched into non-operating position and adapted for actuation by a motor rendered operative by a pedal-actuated electromagnetic clutch, the combination therewith of, a series-connected reduction gear unitary with the electromagnetic clutch, an output shaft driven by and extending from said reduction gear, a presser foot actuating member, and a curved crank drive intermediate and interconnecting said output shaft and presser foot actuating member.

3. In the automatic presser foot shifting mechanism as set forth in claim 1, including, a cam disc mounted on said output shaft, a pair of end switches, an actuating member actuated by said cam disc for actuating one of the end switches into off position when the presser foot is down and for actuating the other of the end switches when the presser foot is up.

4. In the automatic presser foot shifting mechanism as set forth in claim 2, including, a cam disc mounted on said output shaft, a pair of end switches, an actuating member actuated by said cam disc for actuating one of the end switches into off position when the presser foot is down and for actuating the other of the end switches when the presser foot is up.

5. In the automatic presser foot shifting mechanism as set forth in claim 3, including, an actuating member for switching the sewing machine into on and ofi positions, a main switch connected in series with the end switches of said pair thereof and actuated by said actuating member, the end switches of said pair thereof being con- 7 nected to said energy source when the sewing machine motor is switched on and off.

6. A presser foot shift device as set forth in claim 2, characterized in that the two end switches are alternately connected to the source of current by the main switch whereby the end switch responsible for raising the presser foot is connected to the current source before the sewing machine is switched on and the end switch responsible for lowering the presser foot is connected to the current source when the sewing machine motor is switched off.

7. A presser foot shift device as set forth in claim 2, including an electrically actuated brake associated with the reduction gear and automatically engaged when the clutch is disengaged from the motor and automatically disengaged when the clutch is connected to the motor with the circuit of said brake being opened and closed by the cam.

8. A presser foot shift device as set forth in claim 2, including switch bridges of the end switches being shifted when the clutch circuit is opened to a position for causing the brake circuit to close.

9. A presser foot shift device as set forth in claim 2,

.including a main switch actuated by the pedal and having two switch bridges, one of the switch bridges serving to open and close the brake circuit and to close and open the clutch circuit, the other of the switch bridges serving to open and close the sewing machine circuit.

10. A presser foot shift device as set forth in claim 2, including an additional end switch for determining an intermediate position of the presser foot.

11. A presser foot adjusting device as set forth in claim 1-0, including an additional end switch actuated by the cam, and an optionally operable electric switch for normally short-circuiting said adidtional end switch and causing said additional end switch to become effective on actuation.

8 12. A presser foot shift device as set forth in claim 11, said optionally operable switch being a toggle switch. 13. A presser foot adjusting device as set forth in claim 11, said end switches being microswitches.

14. A presser foot shift device as set forth in claim 13, the sewing machine circuit including a closed-circuit relay whose contact prevents the presser foot from being raised before the sewing machine has come to a halt.

15. A presser foot shift device as set forth in claim 14, the sewing machine circuit including a safety switch closed by displacement, caused by the cam of the actuating member when the presser foot is in lower position'for opening the end switch associated with the lower position of the presser foot and disposed in the magnetic clutch circuit.

16. A presser foot shift device as set forth in claim 15,

the end switches and the cam being accommodated in one end cover of the housing for the reduction gear, with another end cover ofsaid housing accommodating a crank drive or eccentric drive.

References Cited by the Examiner UNITED STATES PATENTS 1,332,511 3/1920 Moflatt et al. 112-239 X 1,383,438 7/1921 Stein 1l2239 1,449,771 3/1923 Merrick 112-239 2,990,795 7/1961 Graham et a1 1l2239 3,051,110 8/1962 Graham et al. 112239 FRANK J. COHEN, Primary Examiner.

DAVID i. WILLIAMOWSKY, P. D. DAWSON,

Assistant Examiners. 

1. IN A SEWING MACHINE, AN AUTOMATIC PRESET FOOT SHIFTING MECHANISM RENDERED OPERATIVE AS THE SEWING MACHINE IS SWITCHED INTO OPERATING CONDITION AND INOPERATIVE AS THE SEWING MACHINE IS SWITCHED INTO NON-OPERATING POSITION AND ADAPTED FOR ACTUATION BY A MOTOR RENDERED OPERATIVE BY A PEDAL-ACTUATED ELECTROMAGNETIC CLUTCH, THE COMBINATION THEREWITH OF, A SERIES-CONNECTED REDUCTION GEAR UNITARY WITH THE ELECTROMAGNETIC CLUTCH, AN OUTPUT SHAFT DRIVEN BY AND EXTENDING FROM SAID REDUCTION GEAR, A PRESSER FOOT ACTUATING MEMBER, AND A STRAIGHT CRANK DRIVE INTERMEDIATE AND INTERCONNECTING SAID OUTPUT SHAFT AND PRESSER FOOT ACTUATING MEMBER. 